Add GetObjectDirectorySize RPC

This RPC will be used to determine if a push will
exceed the size limit of a repository.
4 jobs for pb-get-object-directory-size-1-19 in 2 minutes and 48 seconds
Status Job ID Name Coverage
  Test
passed #234501067
build

00:01:49

passed #234501068
check-grpc-proto-clients

00:01:45

passed #234501069
danger-review

00:01:00

passed #234501066
test

00:02:48